The present invention relates to medical image-based estimation of mechanical tissue properties and more particularly to automatic estimation of shear modulus and viscosity of tissue from shear wave imaging.
Shear-wave imaging (SWI) is an ultrasound-based imaging modality that can provide important information about tissue structure and integrity. In SWI, an ultrasound probe is used to generate and track propagating shear waves in biological tissue. Radiation force from an acoustic radiation force impulse (ARFI) generates the shear waves in the tissue. The velocity of the shear wave propagation in the tissue is measured and a time sequence of images showing the displacement of the shear wave is captured by the ultrasound probe.
Qualitative metrics have been derived for SWI, for example to highlight stiffer or softer tissues in a region of interest. Clinical applications for SWI are numerous, especially in oncology where SWI can be used to discriminate malignant from benign lesions. However, accurate quantitative estimation of tissue elasticity and viscosity from SWI remains an important challenge. While shear modulus can be directly related to the shear wave velocity in homogenous isotropic solids, that relationship does not hold in viscous media like biological tissues where the viscosity also affects the speed of the shear wave. It is therefore important to consider both properties in the estimation process in order to achieve accurate assessment of the tissue mechanics and constitution of the tissue.